Compressor governor



April 21, 1936. I 'J c, McCUNE 2,038,185

COMPRESSOR GOVERNOR Filed Jan. 25, 1954 POSITION N l Posrnow N92 srnoN N93 P05) TIO N N FOSITIO N N J4. J7 8 /a Posh- 0N N POSITION N POSITION N 3 INVENTOR l 4 QOSEF'H QMcCUNE A TTORNEY Patented Apr. 21, 1936 UNITED STATES PATENT OFFICE The Westinghouse Air Brake Company,

Wil-

merding, Pa., a corporation of Pennsylvania Application January 25, 1934, Serial No. 708,243

19 Claims.

This invention relates to apparatus employed on electric railway vehicles for compressing fluid for use in controlling the fluid pressure brakes.

On vehicles equipped with a fluid compressor,

a governor device is provided which is adapted, upon a predetermined reduction in pressure in the main or storage reservoir, to effect the starting of the compressor. When the compressor is thus started, it continues to operate until the main reservoir pressure has increased to a predetermined maximum pressure, at which time the compressor governor operates to effect the stopping of the compressor. It is often undesirable to have the compressor running at full speed while the vehicle is standing or coasting, since the noise produced by the running of the compressor is more noticeable at this time and is therefore apt to be objectionable.

The principal object of the invention is to provide automatic means adapted to cause the compressor to run at reduced speed while the vehicle is standing or coasting, and then only when the main reservoir pressure has been reduced to a predetermined low degree, and to run at full speed when current is being supplied to the vehicle motors for propelling the vehicle.

Not only is it undesirable to have the compressor running at full speed while the vehicle is standing but it is also often undesirable to have the compressor running at full speed when the vehicle is being propelled at a low speed, as the vehicle may be so quiet in operation at this low speed that the noise produced by the running of the compressor at full speed may be annoying. At the higher vehicle speeds, the noise produced by the running of the vehicle itself may be so great that the noise incident to the operation of the compressor may not be objectionable.

Another object of the invention is to provide automatic means adapted to cause the compressor to run at reduced speed while the vehicle is standing or coasting and for preventing the compressor from running at full speed until the voltage of the current supplied to the car motors is increased to a predetermined degree, such as will cause the car to be propelled at a relatively high speed.

In the accompanying drawing; Fig. 1 is a diagrammatic view of a fluid compressing apparatus embodying the invention; and Figs. 2 and 3 are similar views, each illustrating another embodiment of the invention.

As shown in Fig. 1, the apparatus comprises a fluid compressor l adapted to be driven by an electric motor 2 and. adapted. to compress fluid through a pipe 3 into a main or storage reservoir 4, a normal compressor governor device 5, an additional compressor governor device 6, and a resistance unit 1.

The normal governor device 5 is shown dia- 5 grammatically as comprising a casing containing a piston 8, subject on one side to the pressure of fluid as supplied from the main reservoir 4 through pipe 9, and subject on the opposite side to the pressure of a spring Ill. The piston 8 car- 10 ries a stem ll having secured thereto a contact member I2 adapted, when the piston is in its innor position, to close a circuit leading to the electric motor 2 which drives the compressor l and to open the circuit when the piston is moved out- 15 Wardly.

The contact member I2 is associated with fixed contacts l3 and I4, the contact [3 being connected to the trolley wire l5 by wire it and the contact I4 being connected by wire I! to the com- 20 pressor motor 2.

The governor device 6 comprises a piston l8 subject on one side to the pressure of fluid as supplied from the main reservoir 4 through pipes 9 and I9, and subject on the other side to the 5 pressure of a spring 20. The piston I8 is provided with a'stem 2| carrying the contact members 22 and 23 which are operable by the piston to also control circuits of the compressor motor 2. The contact member 22 is adapted, when the piston is in its inner position, to close a circuit from the compressor motor'to the resistance unit I, and to open said circuit and close a circuit from the compressor motor to a contact 33 in the usual power controller 24 by way of wire 34 when the piston is in its outer position.

The contact member 22 is associated with the fixed contacts 25 and 26 and the contact member 23 is associated with the fixed contacts 21 and 28. The contact 25 is connected by wire 29 to wire 30 leading to the compressor motor and the contact 22 is connected by wire 3| to one terminal of the resistance unit 1, the other terminal of which is connected by wire 32 to ground. The contact 21 is connected to wire 30 and the contact 28 is connected to contact 33 in the power controller 24.

A contact 44 is provided in the power controller 24 which is movable with the usual power controller contact 36 controlling the car motor circuits, said contact 44 being adapted, in all power on positions of the controller, to close a circuit from the contact 33 to a grounded contact 45 and, in power off position, to open said circuit, for

a purpose which will presently appear.

In operation, assume that the governor device 5 is adjusted for controlling the compressor motor 2 within the usual maximum and minimum pressure range as ordinarily employed, and that the governor device 6 is adjusted so that the piston I8 will not move to its inner position until the pressure in the main reservoir has been reduced to a predetermined low degree, which is lower than the pressure at which the governor device 5 operates to cut in the compressor motor but which is suflicient to insure ample main reservoir pressure for operating the brakes to hold the car while standing. Assume further that the governor device 6 is adjusted so that the piston will move to its outer position at a lower pressure than that at which the piston 8 of the governor device 5 cuts out the compressor motor.

In initially charging, with the power controller 24 in power ofi" position and with the governor device pistons 8 and !8 in their inner positions, as shown in Fig. 1, a circuit is completed from the trolley wire I5 to the compressor motor 2 and thence to the resistance unit 1 by way of wire I6, contacts I3 and I4 and contact member I2 associated with the governor device 5, wire I1, the compressor motor 2, wires 36 and 29, contacts 25 and 26 and contact member 22 associated with the governor device 6, and wire 3I. With the compressor motor circuit thus closed, said motor will run at a speed limited by the resistance unit I, which may be of such a resistance as to limit the speed to, say, half normal speed.

Now, when the pressure of the fluid supplied by the compressor to the main reservoir 4 has been increased to a predetermined degree, the piston I8 of the compressor governor device 6 is moved outwardly, causing the contact member 22 to open the circuit from the compressor motor 2 to the resistance unit I and the contact member 23 to close the circuit from the compressor motor to the contact 33 in the power controller 24, which circuit includes wire 30, contacts 27 and 28, contact member 23 and wire 34. With the controller in power off position, the contact 44 is out of engagement with the contact 33, as hereinbefore explained, so that the circuit just mentioned is open. With the compressor motor circuit thus open, said motor stops running.

When the contact 36 in the power controller 24 is moved to a power on position for supplying current to the usual car motors 35 for propelling the car, a circuit is closed from the fixed contact 31 to one of the fixed contacts 38, 39 and 40, depending upon which power on position is selected. If, for instance, the contact 36 is moved to power on position No. 1, a circuit is closed from contact 31 to contact 38, and with the contact 44 bridging the contacts 33 and 45, current is supplied from the trolley wire I5 to the car motors 35 through a circuit which includes wires I6 and 4!, the motors 35, wire 42, contacts 37, 36 and 38, all of the starting resistance unit 43, and contacts 33, 44 and 45. It should here be understood that the resistance unit 43 represents the usual starting resistance in the car motor circuit and is shown, for the sake of simplicity, as controlled directly by the power controller. As is well known, however, the starting resistance may be controlled by other means, such as, for instance, by relays controlled by a master controller.

With the contact 44 bridging the contacts 33 and 45, current is now supplied from the trolley wire I5 to the compressor motor 2 through a circuit which includes wire I6, contacts I3, I4 and I2 of the governor device 5, wire H, the compressor motor 2, wire 30, contacts 27, 28 and 23 of the governor device 6, wire 34, and contacts 33, 44 and 45. With current at full voltage thus supplied to the compressor motor, said motor will run at full speed. I

If the contact 36 of the power controller 24 is moved to power on position No. 2, a circuit is closed from contact 31 to contact 39, and with the contact 44 bridging contacts 33 and 45, the circuit through the car motors now includes only a portion of the resistance unit 43 and the car motors will therefore drive the car at a faster speed than when the controller is in position No. 1. Similarly, with the contact 36 in position No. 3, a circuit is closed from contact 31 to contact 46, thereby cutting all of the resistance unit 43 out of the car motor circuit, so that the car motors will propel the car at a faster speed than when the controller is in position No. 2.

Since in all power on positions of the controller the contact 44 connects contacts 33 and 45, the compressor motor will run at full speed until the pressure of the fluid in the main reservoir has been increased to the cutting-out point of the governor device 5, when the piston 8 of said device will be moved to its outer position, causing the contact member I2 to open the compressor motor circuit.

It will be evident that since the cutting-in pressure of the governor device 5 is higher than the cutting-in pressure of the governor device 6, the high pressure governor device 5 will control the operation of the compressor motor while the power controller is in a power on position.

When the power controller 24 is moved to ofi position, as shown in Fig. 1, the contact 44 is shifted so as to open the circuit from the contact 33 to the contact 45, so as to break the circuit through which current at full voltage is adapted to be supplied to the compressor motor. If at this time, the pressure of the fluid in the main reservoir 4 has been reduced to a predetermined degree, the high pressure governor 5 operates to move the contact member I2 into engagement with the contacts I3 and I4. Current is not supplied to the compressor motor, however, until the pressure of the fluid in the main reservoir is still further reduced to the cutting-in pressure of the low pressure governor 6, at which time the piston I8 is shifted so as to cause the contact member 22 to connect the contacts 25 and 26. With said contacts thus connected, the circuit is closed from the trolley wire I5 through the compressor motor 2 and the resistance unit 1, which circuit includes wire l6, contacts I3, I4 and I2 of the high pressure governor 5, wire I l, the compressor motor 2, wires 36 and 29, contacts 25, 26 and 22 of the low pressure governor 6, wire 3| and the resistance unit 1. With the compressor motor circuit thus closed, the compressor motor will run at a speed determined by the resistance unit I, as in the initial charging operation hereinbefore described.

It will be seen from the foregoing that the compressor is adapted to run at full speed when the car is being propelled and is adapted to run at a reduced speed when the caris standing or is coasting.

The apparatus shown in Fig. 2 comprises a high pressure compressor governor 5, a low pressure compressor governor 50, a resistance unit 51 and a relay device 5|.

The high pressure governor 5 may be adjusted to operate at the usual pressures for moving the contact member I2 into and out of engagement with the contacts I3 and M. The low pressure governor is adjusted so that the contact member 52 will not engage the contacts 53 and 54 until the main reservoir pressure has been reduced to a predetermined low degree, which is lower than the pressure at which the high pressure governor 5 operates to close the circuit from the contact i3 to the contact M.

The contact 53 is connected by wire 55 to the trolley wire l5 and the contact 54 is connected by wire 55 to one terminal of the resistance unit 51, the other terminal of which is connected by wire 58 to the contact i3 of the high pressure governor 5. The other contact I4 of said governor is connected by wire 59 to the compressor motor 2.

The relay device 5| comprises the switch contacts 50 and 6| controlled by a switch member 62 carried by a solenoid core 63 which is controlled by a coil (i l, one terminal of which is connected by wire 55 to the supply wire 66 leading to the car motors 35 and the other terminal or" which is grounded, in this instance by the wire 61 which connects with the ground wire 58 of the car motors 35. The contact 50 is connected by wire 59 to the wire 58 and the contact 6| is connected by wire '10 to the wire 55. The switch member 62 is normally maintained in open position, in this instance by the weight of said switch member and the core 63. It should be understood that the relay device is responsive only to current of a predetermined voltage for moving the switch member to closed position.

With the usual power controller 24 in a power on position for supplying current to the car motors 35 for propelling the car, the contact 36 on the controller drum closes the circuit from the fixed contact 31, which is connected by wire to the wire 55, to one of the fixed contacts 38, 39 and 40, depending upon which power on position is selected. In power on position No. 1, the contact 35 bridges contacts 31 and 38, so that current is supplied from the trolley wire I5 to the car motors through a circuit which includes wires 55 and H, contacts 3'l', 35 and 38, all of the starting resistance 43, and wire 65. In power on position No. 2, with the circuit completed, through contact 35, from contact 31 to contact 38, current is supplied to the car motors through only a portion of the resistance 53, and in power on position No. 3, all of the resistance 43 is out out of the car motor circuit, so that current at full voltage is supplied to the car motors. Thus, the voltage of the current supplied to the car motors, and consequently the speed of said motors, varies according to the amount of the resistance 43 in the motor circuit.

Current supplied to the wire 66 leading to the car motors 35 also flows through wire 55 to the coil 34 of the relay device 5| and thence through wires 61 and 68 to ground, with the result that said coil is energized. When the voltage of the current supplied to wire 65 is increased to a predetermined degree, by varying the amount of the resistance 43 in the motor circuit, as above described, the coil 64 is energized sufliciently to cause the core 63 to operate and shift the switch member 52 to closed position, in which a circuit is closed from wire 55 to the contact l3 in the high pressure governor 5 through wire 10, contacts 6! and 6| and switch member 62 in the relay device 5|, and wires 59 and 58. The high pressure governor 5 then controls the operation of the compressor, in the usual manner.

Thus, only when the car is being propelled at a relatively fast speed, is current at full voltage adapted to be supplied to the compressor motor for driving said motor at full speed, and at this time the high pressure governor controls the operation of the compressor.

When the power controller drum is moved to oif position, the contact 35 opens the energizing circuit through the coil 64, with the result that said coil becomes deenergized and the core 63 then shifts the switch member 62 to open position, so as tocut oh the supply of full voltage current to the high pressure governor 5.

When the pressure in the main reservoir 4 has been reduced to a predetermined degree, the compressor governor 5 operates to its cut-in position, in which the contact member l2 bridges the contacts l3 and I4 and upon a still further reduction in main reservoir pressure to a predetermined low degree, the low pressure governor 50 operates to its cut-in position, as shown in Fig. 2, so as to cause the contact member 52 to bridge the contacts. 53 and 54. A circuit is thus established from the trolley wire |5 to the com pressor motor 2 through the resistance unit 51, which circuit includes wire 55, contacts 53 and 54 and contact member 52 in the low pressure governor 50, wire 55, resistance unit 51, wire 58, contacts i3 and M and contact member l2 in the high pressure governor 5, and wire 59. With the compressor motor circuit thus established,

the compressor motor will operate at a speed determined by the resistance unit 51. Thus, the compressor is adapted to operate at reduced speed when the car is standing or is coasting.

It should be noted that until the voltage of the current supplied to the car motors is increased to a degree sufiicient to cause the relay device 5| to operate to close the circuit to the compressor motor 2 for supplying full voltage current to said motor, the low pressure governor controls the circuit to the compressor motor through the resistance unit 51, and therefore when said governor operates to cut-in position, current at reduced voltage is supplied to said motor. Thus, at relatively slow car speeds, the compressor motor is adapted to run at a low speed.

The apparatus shown in Fig. 3 comprises a compressor governor 5, a resistance unit 5? and a relay device 5|.

The compressor governor 5 may be adjusted to operate at the usual pressures for shifting the contact member |2 into and out of engagement with the contacts l3 and M. The contact 53 is connected to wire 55 and the contact I5 is connected to the compressor motor 2 by wire 12.

One terminal of the resistance unit 51 is connected to the compressor motor 2 by wire 73 and the other terminal of said unit is connected to the grounded wire '54.

The contact 65 of the relay device 5| is connected by wire 15 to wire 13 and the contact 6| of said relay device is connected to the grounded wire M. One terminal of the coil 64 is connected by wire 15 to the supply wire Tl lead ng to the car motors 35 and the other terminal of said coil is connected to ground by wire 18.

With the power controller 25 in a power on position, the contact 36 on the controller drum controls the flow of current to the car motors 35 through the wire Tl in the usual manner and the coil 64, being connected to the motor circut as above explained, is energized by this flow of current. When the voltage of the current supplied to the car motors is increased to a predetermined degree, the coil 64 becomes energized sufficiently to cause the core 63 to operate and shift the switch member 62 to closed position. Thus, a circuit is established from the contact 14 in the compressor governor 5 through the compressor motor by way of wire 12, the compressor motor, wires 13 and 15, contacts 60 and BI and switch member 62 in the relay device 5|, and the grounded wire 74. The compressor governor 5 will then operate in the usual manner to control the supply of full voltage current to the compressor motor so long as the relay device 5| remains in the circuit closing position.

When the power controller drum is moved to off position, the energizing circuit through the coil 64 is opened and the resulting deenergization of said coil causes the core 63 to operate and shift the switch member 62 to open position, so as to open the circuit through which full voltage current is supplied to the compressor motor. With said circuit thus opened, the compressor governor 5 controls a circuit through the compressor motor, which circuit includes wire 55, contacts l3 and I4 and contact member in the compressor governor 5, wire 12, the compressor motor 2, wire 13, resistance unit 51 and the grounded wire Hi. When the compressor governor operates to close this circuit, the compressor motor will run at reduced speed, as determined by the resistance unit 57.

It will be seen that when the voltage of the current supplied to the car motors is not suflicient to move the relay device 5| to the circuit closing position for supplying full voltage current to the compressor motor, current at reduced volt age is adapted to be supplied to said motor, through the resistance unit 51.

Thus, when the car is standing or coasting or is being propelled at a relatively slow speed, the compressor motor is adapted to run at reduced speed but when the car is running at relatively high speeds, the compressor motor is adapted to run at full speed.

While one illustrative embodiment of the invention has been described in detail, it is not my intention to limit its scope to that embodiment or otherwise than by the terms of the appended claims.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

l. The combination with a vehicle having a driving motor and a power controller .for said motor having power on and power ofi positions, a compressor, a motor for driving said compressor, of means for supplying current at one voltage to the compressor motor in a power on position of said controller, and means operated upon a fall in the pressure of fluid compressed by sa'd compressor to a predetermined degree, when said controller is in a power off position, for supplying current at a lower voltage to said compressor motor.

2. The combination with a vehicle having a driving motor and a power controller for said motor having power on and power off positions, a compressor, a motor for driving said compressor, of means operated upon a fall in the pressure of the fluid compressed by said compressor to a predetermined degree when said controller is in power off position for supplying current at one voltage to the compressor motor, and means operated upon an increase in the pressure of the fluid compressed by said compressor to a predetermined degree when said controller is in a power on position for supplying current at a higher voltage to said motor.

3. The combination with a vehicle having a driving motor and a power controller for said motor having power on and power off positions, a compressor, and a motor for driving said compressor, of. means automatically operative at one time to supply current of a given voltage to the compressor motor and operative upon an increase in the pressure of the fluid compressed by said compressor to a predetermined degree, when said controller is in a power on position, to supply current at a higher than said given voltage to said compressor motor.

4. The combination with a vehicle having a driving motor and a power controller having power on and power off positions, a compressor, and a motor for driving said compressor, of means operative, when said controller is in a power on position and the pressure of the fluid compressed by said compressor is reduced to a predetermined degree to supply current at a given voltage to the compressor motor, said means being also operative to supply current to the compressor motor at a lower voltage when the pressure of the fluid compressed by said compressor is reduced to a predetermined pressure less than the pressure at which said means operates to supply current of said given voltage to said motor.

5. The combination with a vehicle having a driving motor and a power controller for said motor having power on and power off positions, a compressor, and a motor for driving said compressor, of a high pressure governor and a low pressure governor cooperative with each other, upon a fall in the pressure of the fluid compressed by said compressor to a predetermined pressure when said controller is in a power on position, for supplying current at a given voltage to the compressor motor, said governors being also cooperative with each other for supplying current at a lower voltage to said motor when a fall in the pressure of the fluid compressed by said compressor to a predetermined pressure less than the pressure at which said governors cooperate to supply current at said given voltage to said motor.

6. The combination with an electric motor driven fluid compressor and a power controller having power on and power off positions, of a high pressure compressor governor having a switch for opening and closing the circuit to the compressor motor, said governor being operated by variations in the pressure of the fluid compressed by said compressor for operating said switch, a resistance unit, and a low pressure compressor governor including switch means series connected in a circuit with said switch and operative to close a circuit to said motor for supplying current at a given voltage to said motor, when said controller is in a power on position, upon an increase in the pressure of the fluid com pressed by said compressor to a predetermined pressure less than the pressure at which the high pressure governor operates to open said switch, said low pressure governor also including other switch means series connected in a circuit with said switch and with said resistance unit and operative to close a circuit to said compressor motor through said resistance unit for supplying current at a lower voltage to said motor upon a fall in the pressure of the fluid compressed by said compressor to a predetermined pressure less than the pressure at which the high pressure governor operates to open said switch, the first mentioned switch means being operative to the circuit opening position upon movement of the second mentioned switch means to the circuit closing position.

7. The combination with an electric motor driven fluid compressor, of means operated upon a fall in the pressure of the fluid compressed by said compressor to a predetermined degree for supplying current at a given voltage to the com pressor motor, and electro-responsive means operated upon a predetermined increase in the voltage of the current supplied thereto tosupply current at a higher than said given voltage to said motor, said electroresponsive means comprising a switch controlling a circuit associated with the compressor motor and having a resistance in series therewith.

8. The combination with a vehicle having a driving motor and a power controller for said motor having power on and power off positions, a compressor, and a driving motor for said compressor, of electro-responsive means operative upon a predetermined increase in the voltage of the current supplied thereto to supply current at one voltage to the compressor motor when said controller is in a power on position, and means operated upon a fall in the pressure of the fluid compressed by said compressor to a predetermined degree to supply current at a lower voltage to said motor.

9. The combination with a vehicle having a driving motor and a power controller for said motor having power on and power ofi positions, a compressor, and a driving motor for said compressor, of electro-responsive means operative upon a predetermined increase in the voltage of the current supplied thereto to supply current at one voltage to the compressor motor when said controller is in a power on position, and means operated upon a fall in the pressure of the fluid compressed by said compressor to a predetermined degree to supply current at a lower voltage to said motor when said controller is in power off position.

10. The combination with an electric motor driven fluid compressor, of electro-responsive means operative upon a predetermined increase in the voltage of the current supplied thereto to close a circuit through which current at one voltage is supplied to the compressor motor, means operative upon an increase in the pressure of the fluid compressed by said compressor to a predetermined degree to open said circuit, and means operated upon a fall in the pressure of the fluid compressed by said compressor to a predetermined degree to supply current at a lower voltage to said motor.

11. The combination with an electric motor driven fluid compressor and a power controller having power on and power off positions, of electro-responsive means operative upon a predetermined increase in the voltage of the current supplied thereto when said controller is in a power on position to close a circuit through which current at one voltage is supplied to the compressor motor, means operative upon an increase in the pressure of the fluid compressed by said compressor to a predetermined degree to open said circuit, and means operated upon a fall in the pressure of the fluid compressed by said compressor to a predetermined degree to supply current at a lower voltage to said motor.

12. The combination with an electric motor driven fluid compressor, of electro-responsive means operative upon a predetermined increase in the voltage of the current supplied thereto, when the pressure of the fluid compressed by said compressor falls to a predetermined degree, to supply current at a given voltage to the compressor motor, and means operative to supply current at a lower voltage to said motor when the pressure of the fluid compressed by said compressor is reduced to a predetermined pressure less than the pressure at which said electroresponsive means is operative to supply current at said given voltage to said motor.

13. The combination with an electric motor driven fluid compressor and a power controller having power on and power off positions, of elecarc-responsive means operative upon a predetermined increase in the voltage of the current supplied thereto tocontrol a circuit through which current at a given voltage is adapted to be supplied to the compressor motor when said controller is in a power on position, a high pressure governor cooperative with said electro-responsive means for controlling said circuit, said governor being operated by variations in the pressure of the fluid compressed by said compressor for opening and closing said circuit, and a low pressure governor operative to supply current at a lower voltage to said motor upon a fall in the pressure of the fluid compressed by said compressor to a predetermined pressure less than the pressure at which the high pressure governor operates to close said circuit.

14. The combination with an electric motor driven fluid compressor and a power controller having power on and power oil positions, of electro-responsive means operative upon a predetermined increase in the voltage of the current supplied thereto to control a circuit through which current at a given voltage is adapted to be supplied to the compressor motor when said controller is in a power on position, a high pressure governor cooperative with said electro-responsive means for controlling said circuit, said governor being operated by variations in the pressure of the fluid compressed by said compressor for opening and closing said circuit, and a low pressure governor operative, when said controller is in power off position, to supply current at a lower voltage to said motor upon a fall in the pressure o f the fluid compressed by said compressor to a predetermined pressure less than the pressure at which the high pressure governor operates to close said circuit.

15. The combination with a vehicle having a driving motor and a power controller for said motor having power on and power ofi positions, a compressor, and a driving motor for said compressor, of means operative in power off position of said controller to supply current at a given voltage to the compressor motor, and electro-responsive means operative upon a predetermined increase in the voltage of the current supplied thereto, when said controller is in a power on position, to supply current at a higher than said given voltage to said motor.

16. The combination with a vehicle having a driving motor and a power controller for said motor having power on and power off positions, a compressor, and a driving motor for said com pressor, of a resistance unit in a circuit with the compressor motor, switch means operated by variations in the pressure of the fluid compressed by said compressor to open and. close said circuit, and electro-responsive means operative upon a predetermined increase in the voltage of the current supplied thereto, when said controller is in a power on position, to close a circuit to said motor independent of said resistance unit.

17. The combination with a vehicle carried fluid compressor, an electric motor for driving said compressor, and motors for driving the vehicle, and a power controller for said vehicle motors having power on and power off positions, of a resistance unit in a circuit with the compressor motor, switch means operated by variations in the pressure of the fluid compressed by said compressor to open and close said circuit, and electro-reponsive means operative upon a predetermined increase in the voltage of the current supplied to said vehicle motors to close a circuit to the compressor motor independent of said resistance unit.

18. The combination with a vehicle having a driving motor and a power controller for said motor having power-on and power-off positions, a compressor, a motor for driving said compressor, of means operative when said power controller is in the power-on position and the pressure of fluid compressed by the compressor is reduced to a predetermined degree to supply current at a given voltage to the compressor motor, said means being also operative to supply current to the compressor motor at a lower voltage irrespective of the position of the power controller when the pressure of the fluid compressed by the compressor is reduced to a predetermined pressure less than the pressure at which said means operates to supply current of said given voltage to said motor.

19. The combination with a vehicle having a driving motor and a power controller for said motor having power-on and power-off positions, a compressor and a motor for driving said compressor, of means operative irrespective of the position of the power controller when the pressure of the fluid compressed by the compressor is reduced to a predetermined degree to supply current to the compressor motor, and means controlled by the power controller and operable on movement of the power controller to a power-on position to effect an increase in the voltage of the current supplied to the compressor motor.

JOSEPH C. McCUNE. 

